Apparatus for the granulometric separation of granular, pulverulent materials

ABSTRACT

An apparatus for the granulometric separation of a granular product in suspension in a liquid, comprising an inclined stationary frame, and a flexible screening cloth supported on and extending across the frame so as to be similarly inclined therewith. A feeding means is positioned at the upper portion of the frame for delivering liquid and granular products suspension to the upper end of the screening cloth. A channel is provided beneath the cloth for receiving the screened liquid, and a channel is provided at the lower end of the cloth for receiving the separated granules.

mte States Patent 1 1 1111 3,712,476

Cohen-Allow et al. 1 Jan. 23, 197 3 [54] APPARATUS FOR THE [56] References Cited GRANULOMETRIC SEPARATION OF UNITED STATES PATENTS GRANULAR,PULVERULENT 275 4/ 8 K 1 ,340 18 3 imbal ..21o/3s9 x MATERIALS 794,631 7/1905 Milne ..,.210/3s7 x 964,897 7/1910 Bryant ..210 389 [76] Inventors: Richard Cohen-Alloro, l, Passage 1,663,164 3/1928 Helman 3 des Geraniums, Orleans; Roger Cufi 1 urs y i i 1: ,de la Fede'amr" 3,363,769 l/l968 Wilmotetal... ....209/353 x 3,477,571 11/1969 Maag ..2o9 273 x Filed: April 14, 1971 App]. No.: 134,052

Related U.S. ApplicationData Continuation 0f Ser. N6. 784,357, Dec. '17, 1968,

abandoned.

Foreign Application Priority Data May 7, 1968 France ..68l50788 U.S. Cl. ..2l0/387, 210/433, 210/456 Int. Cl. ..B0ld 29/04 Field Of Search ..209/273, 315, 352, 353, 401, 209/403; 210/77, 387, 389, 499, 433, 456

Primary ExaminerSamih N. Zaharna Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT 7 Claims, 12 Drawing Figures PATENTEDJAN23 I975 I 3'712'478 sum 1 or 2 V PATENTEDmzs 1975 3.712476 sum 2 or 2 SEPARATION OF GRANULAR, PULVERULENT MATERIALS CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of application Ser. No. 784,357 filed Dec. 17, 1968, now abandoned.

The present invention concerns an apparatus for the separation of a crude, granular pulverulent or clay-like mixture in a moist medium, said apparatus. having a fixed screening dimension, This invention also concerns the process employed which makes it possible to achieve such separation through a very fine mesh, with great screening precision and giving considerable yields. a

Conventional apparatus for the separation of granules generally have limits in use set by the size of particles to be separated, by the precision andyield of the separation, or by the delivery which decreases at the same rate as the 'screeningdimension decreases.

Therefore industrial filters, plane grids and curved grids usually process coarse feeds, greater than 100 microns. Y

Other apparatus can furnish separations of finer dimensions such as hydroclassifiers or hydrocyclones,

but apart from the fact that the feed must be conditions intended to eliminate the coarser fractions, the screening finally obtained is not precise and an occationed by one or more preliminary calibration operasionally large proportion of the finer fraction is carried away with the larger fraction.

Thus, in industry, on account of the large deliveries required, it has only been possible'to operate on cloths having relatively large meshes of the order of 0.1 mm, and generally above, and by using a dynamic screening process: by vibration, jolts, oscillation or rotation, thus necessitating expensive and bulky equipment.

Conversely, fine mesh cloths are used inthe laboratory without the use of a dynamic process, for the treatme'nt of very small quantities of substances. This static filtration process is not able to meet the requirements of industry, since, in fact, one is limited not only by the time, but also by the absence of resistance of fine mesh cloths and by their premature wear'. Since they are able tojwithstand only small loads, the filters can have only small dimensions: 20 cm in diameter, for example, a feature which precludes any" industrial application because the quantitiesof products of to be treated in naturally granular, pulverulent or clay-like products, according to which process, the pulp is fed on a flexible or elastic system substantially comprising a woven cloth, preferably of plastic material, acting as a filter, also characterized by its mesh aperture, selected as required from one of the various specifications offered by the trade, resting by the whole or part of its length on or below a thick layer of a cellular porous plastic material of polyester type, or any other type having sufficient characteristics of elasticity and porosity, said system being supported by an inclined frame of variable slope, the combination of mesh' aperture of the cloth and the slope of the frame combining to obtain the desired granulometric screening.

Thus, even though a very fine mesh filter cloth is used, it has now become possible to increase its dimensions and to pour large quantities of products onto it. Furthermore, experience hasshown that, by inclining the filter cloth, it is possible to obtain a granulometric screening of very great precision, the dividing curve approximating to a broken right-angled line, consequently corresponding to perfect screening with the selected mesh, while the outline of the dividing curve of a conventional hydroclassifier has a more or less elongated curved form corresponding to a not inconsiderable percentage of unfiltered substance of a size smaller than the mesh concerned.

Another object of the present invention concerns an apparatus for granulometric separation employing the above-described process, capable of obtaining fine screenings giving a great yield and of a pre-dete'rmined size, capable of starting exactly from 30 microns, comprising an inclined frame having an adjustable-slope, a filter cloth, means for distributing the kinetic energy of the'wave of pulp over the entire extent of the upper part of the cloth, means for distributing the pulp over the entire cloth, as also means for making it possible to bring the portion of the cloth subjected to intense filtration into an area where less work is being performed or to remove this area completely. I

The principal advantage of this construction isan increased yield of the apparatus, the pulp circulating over the entire surface of the filter. Moreover, since the filter cloth can be moved it is no longer necessary, as is industry may amount to as much as 100 cubic meters for separating into granules a mixture, suspended in water or in any other liquid, of crushed or naturally granular, pulverulent or clay-like products, characterized in that it substantially comprises a flexible filter cloth having a conventional mesh aperture, an inclinable frame to maintain the position of the said filter cloth and to give it the desired incline, a feed channel in the upper. part of thesaid frame, a channel for the recovery of the filtered products below the frame and a channel for the screen reject downstream of thecloth.

Another object of the present invention concerns a new apparatus for the granulometric separation or concentration of pulp, that is to say, of a mixture, in

suspension in water or in any other liquid, of crushed or the case with previous filters, to change an entire filter cloth which is worn only in'one place, thus involving a prohibitive waste of time. According to the present invention, it is only necessary, even whilst operation is still proceeding, to move the cloth by winding it round a reel located above it, so that only the part situated in the area in which filtration is most intense and, consequently, where the cloth becomes soonest worn, is

removed as desired, rapidly, without stopping work, and very economically, this arrangement is of special advantage in cases where it is a matter of concentration or. separation with the desired size of granule, of a large quantity of pulp in the shortest possible time.

Another object of the present invention concerns an apparatus comprising, in addition to the inclinable frame and the filter cloth, an absorber pad, in contact with the cloth in order to eliminate the effects of capillary action resisting the free flow of the pulp, particularly argilacious pulp, as also conduits ensuring the elimination ofaccumulations of v substances, the dilution thereof, the addition of conditioning reactance to complete the action of the absorber pad by improved distribution over the cloth.

In this manner, rejects resulting from capillary action are avoided, thereby increasing the screening precision and simultaneously the delivery of the apparatus, since the entire surface of the filter cloth is fully utilized.

In order that the invention may readily be carried into practice, various embodiments will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of the apparatus in section, illustrating the principle of the invention.

FIG. 2 is a plan view of the apparatus shown in FIG. 1.

FIG. 3 is a schematic view in section of an embodiment of the present invention, the cloth being disposed on a non-elastic support.

FIG. 4 is a variant of the apparatus shown in FIG. 3.

FIG. 5 is a schematic view in section of an apparatus similar to the foregoing in which the cloth also rests on a porous and elastic member.

FIG. 6 is a schematic view in section, showing a device in which the cloth is partly below a porous elastic layer.

FIG. 7 is a schematic view in section of a variant of the apparatus shown in FIG. 6, in which the cloth is covered by a protective member.

FIG. 8 is a schematic ,view in section of an apparatus similar to that shown in FIG. 7, fitted with an initial screening grid.

FIG. 9 is a scematic view in section of an apparatus in which the cloth can be moved as desired.

FIG. 10 is a schematic view in section of a release container for feeding the apparatus.

FIG. 11 is a schematic plan view of the container,

and

FIG. 12 is a partial schematic view in section showing an arrangement of spray nozzles.

FIG. 1 shows the section taken on the lines A-A of the apparatus shown in plan in FIG. 2. With reference to these figures the cloth 1 is shown simply stretched in the inclined frame 2 of the apparatus. The pulp to be processed is fed by a feed channel 3 and falls on to the entire width of the upper portion of the cloth. The liquid, charged with particles of smaller dimensions than the opening of the mesh, passes through the cloth and is recovered by the channel 4, whilst the portion refused by the sifter slides over the cloth and is recovered by the channel 5.

The slope of the cloth is selected dependently on the screening position with the desired mesh, on the characteristics of the pulp, in particular on the shape of the granules: angular as in the case of quartz for example, round as in the case of garnets or flat as in the case of mica, and on the desired yield. Since the device enabling the frame or the apparatus to be inclined, may be of any desired type, it has not been shown.

Although such apparatus is already giving remarkable results with certain types of pulp, the yield thereof is improved by disposing the cloth 1 on a support formed by a barred grid 6 (FIG. 3).

The contact points between the bars and the cloth ensure a certain degree of relief, creating multiple slight waves assisting drainage. Moreover, since the formation of a center area is avoided in which the pulp could dig a pocket in the cloth, an improved yield of the apparatus is obtained, since the pulp no longer tends to accumulate in the center area. Improved distribution of the pulp on the surface of the cloth also makes it possible to increase the delivery of substances to be processed.

As a variation, it is also possible to rest the cloth 1 (FIG. 4) on a simple wire gauze 7 having a mesh aperture greater than that of the cloth I and stretched over the frame 2. For example, the wire gauze may have a mesh aperture of 1 mm. For the sake of clarity, the cloth 1 is shown above the grid 7, but in fact the cloth rests completely on the grid.

Experience has shown that the yield of the apparatus is further increased by disposing the sifting cloth 1 directly on an elastic porous layer 8 (FIG. 5). This layer may be supported by a grid such as 6 and preferably by a wire gauze such as 7 so as to produce a close contact between the pad 8 and the cloth 1.

In fact, in addition to the damper part played by the pad 8, the close contact it produces with the cloth makes it possible to overcome the effects of capillary action of the cloth which, according to the viscosity of the pulp, would tend to reject a portion of the pulp and, consequently, to create preferential passages for the pulp on the cloth.

In the event of the deliveries becoming greater, an extra layer 9, as shown in FIG. 6 of an elastic, porous material is added above the cloth and at the level of its upper portion. This layer avoids the direct impact of the flow of pulp onto the cloth which can then work normally at this place.

When the deliveries become even greater, it has been found that the presence of a grid 10 (FIG. 7), disposed directly on the cloth I, and possibly on the layer 9 and the cloth 1, plays the simultaneous role of a means of protecting the cloth and regulating the discharge of the pulp which, by spreading over the entire surface of the cloth, again increases the yield of the apparatus.

In the event of the pulp containing large particles, a mesh or bar grid 11 (FIG. 8) is provided intended for initial screening. Contrary to the other members which are in contact with the cloth 1 the grid 11 is located with a certain clearance above the cloth, thus playing the simultaneous role of initial screen and protector.

However, even when the arrangement shown in FIG. 8 is adopted, non-uniform wear of the cloth will be ascertained by reason of the appreciable differences between the quantities filtered along the surface. In particular, since area adjacent to the area 3 (FIG. 1) is an area in which filtration is most intense, this part of the cloth tends to wear or warp prematurely. Therefore, instead of changing the cloth, a feature which involves considerable loss of time, according to the invention, a roll of cloth 13 (FIG. 9) is located below the frame which roll is unwound by winding the portion of cloth disposed between the layer 8 and the grid 10 on the roll 12 located above the frame. As required, the rolls l2 and 13 may be driven continuously automatically or otherwise. The cloth which is not worn out, but only warped, may then be renovated. This arrangement is of particular advantage when the deliveries become large and great screening precision is desired.

When this is the case, the flow of pulp is fed into a release container 14, shown only schematically in FIGS. and 11. The generally tubular flow is circulated through a series of bafi'les, such as 15, and penetrates to the outlet of the container in the sealed frames 16 through a passage having a very elongated section, thus distributing the flow of pulp over the entire width of the frame. I

Within the frame a series of spray nozzles 17 are arranged, above the cloth 1. They may be fed with compressed air, water, with a reactant or a solution to be processed. As required, they assist in completing the washing or increasing the delivery of the apparatus or in forcing the evacuation of the rejected material or assisting the unwarping action, it being possible to com bine these various actions, according to the case.

The construction of such an apparatus has made it possible to process a larger number of products and, particularly, clay-like products containing, in addition to clay, large particles of quartz, silica and other coarse impurities extending in dimension from 0 to 10 mm, in a concentration which, for example, has been fixed between 50 and 250 g/l.

A single passage of such a product over such an apparatus as described above and fitted, as required, with a cloth of 81 microns, 104 microns or 124 microns, has

made it possible to obtain screenings leading to the recovery, quasi quantitative, of clay and its separation from coarse fractions greater than the openingof the screen-The outline of the dividing curve approximate to a broken right-angled line, a feature which demonstrates the advantage of the process relatively to conventional hydroclassifiers or graders for which the dividing curve assumes a more or less incline form.

it is important to note that, since separation begins as soon as the apparatus is fed, said apparatus may be used both for industrial operations which are continuous and for prospecting campaigns or for intermittent adjusting operations.

Although only one embodiment of the present invention has been described, together with certain variants, it is clear that numerous additions, substitutions or omissions could be made with regard to the various members of the apparatus without departing from the object of the present invention. For example, the frame supporting the screening system could be arched or have aparticular shape with an obtuse angle or a convex or concave curve or in parallel planes in several.

may have a different shape or design, whilst retaining the described object. Similarly, the nature of the material forming the frame of the screen, as also the various metal parts of the apparatus may be adapted to different conditions of use, by utilizing for example alioys resisting sea water corrosion if the prospecting is,

tending across said su port said frame and sup ort having cavltles larger t an t e openings in said c oth,

feeding means at the upper portion of said frame for delivering the liquid and granular product suspension to the upper end of said screening cloth, a layer of an elastic porous cellular material disposed over the upper end portion of said cloth beneath said feeding means, means beneath said screening cloth for receiving the screened liquid, and means at the lower end of said cloth for receiving the separated granules on said cloth.

2. An apparatus as claimed in claim 1, wherein said support comprises a thick elastic layer of a porous cellular material.

3. An apparatus as claimed in claim 1 also comprising deflector means for distribution the flow of the liquid and granular product suspension over the entire extent of the upper end of said screening cloth.

4. An apparatus as claimed in claim 1, wherein said support comprises a screening grid and a layer of a porous cellular material said cloth resting on said elastic layer.

5. An apparatus as claimed in claim 14, comprising at least one initial screening grid mounted on said frame above the cloth.

6. An apparatus as claimed in claim 5 also comprising a series of spray nozzles above the said cloth for assisting in the screening of said granular product.

7. An apparatus as claimed in claim 6 comprising a lower roll from which the said cloth isunwound and an upper roll on which it is wound, said rolls being mounted on said frame. 

1. An apparatus for the granulometric separation of a granular product in suspension in a liquid, comprising an inclined stationary frame, a support extending across said frame so as to be similarly inclined therewith, a flexible screening cloth resting on and extending across said support, said frame and support having cavities larger than the openings in said cloth, feeding means at the upper portion of said frame for delivering the liquid and granular product suspension to the upper end of said screening cloth, a layer of an elastic porous cellular material disposed over the upper end portion of said cloth beneath said feeding means, means beneath said screening cloth for receiving the screened liquid, and means at the lower end of said cloth for receiving the separated granules on said cloth.
 2. An apparatus as claimed in claim 1, wherein said support comprises a thick elastic layer of a porous cellular material.
 3. An apparatus as claimed in claim 1 also comprising deflector means for distribution the flow of the liquid and granular product suspension over the entire extent of the upper end of said screening cloth.
 4. An apparatus as claimed in claim 1, wherein said support comprises a screening grid and a layer of a porous cellular material said cloth resting on said elastic layer.
 5. An apparatus as claimed in claim 14, comprising at least one initial screening grid mounted on said frame above the cloth.
 6. An apparatus as claimed in claim 5 also comprising a series of spray nozzles above the said cloth for assisting in the screening of said granular product.
 7. An apparatus as claimed in claim 6 comprising a lower roll from which the said cloth is unwound and an upper roll on which it is wound, said rolls being mounted on said frame. 